In RMX (I don't know specifically about Superior Drummer) you need to go to the Mixer page (IN RMX) and each Channel/part is set by default to Output A. Click to assign one of the channels to a different Output e.g. B, C, D.
Now in Logic's Mixer, click on the + button to create Aux's relating to those outputs.
The newly created Aux's will display the Input as Stylus RMX 3-4, etc.
This is in Logic 9.0.1.